1. Field of the Invention
The invention relates generally to efficient means for utilizing energy from subterranean geothermal sources and, more particularly, relates to novel arrangements including efficient deep well heat exchange and pumping equipment for pumping of underground water to the earth's surface.
2. Description of the Prior Art
A basic advance in the geothermal power extraction art was presented in the U.S. Pat. No. 3,824,793 issued to H. B. Matthews on July 23, 1974 for a "Geothermal System and Method", and the divisional application which resulted in the U.S. Pat. No. 3,898,020 of the same title issued Aug. 5, 1975, both of which were assigned to the Assignee of the instant invention. The aforementioned patents disclose geothermal energy recovery systems making use of thermal energy stored by subterranean heat sources in hot, solute bearing well water to generate a vapor from a surface injected flow of working fluid, for example, water; the vapor being used to operate a turbine driven pump within the well for pumping the hot geothermal fluid or brine at high pressure and always in liquid state to the earth's surface, where transfer of its heat energy in a binary closed loop heat exchanger is effected to vaporize a second fluid to drive a turbine-alternator combination for the generation of electrical power. The residual brine is pumped back into the earth, while the working fluid is regenerated at the surface and returned to the deep well pumping system for generating vapor and lubrication of fluid bearings supporting the turbine driven pump system.
An improvement in the basic Matthews concept appears in a more recently issued U.S. Pat. No. 4,142,108, issued Feb. 27, 1979 to H. B. Matthews for a "Geothermal Energy Conversion System". In this patent, the solute bearing hot well water is pumped upward to the earth's surface through an extended lineal heat exchange element for continuously heating a downward flowing organic working fluid. The temperature difference between the upward flowing brine and the downward flowing organic working fluid is maintained finite in a predetermined manner along the length of the subterranean extended heat exchange element wherein the working fluid is pressurized due to the gravity head as it flows down the lineal heat exchange element. After driving the deep well turbine driven pump, the hot organic fluid rises in a thermally insulated conduit for driving electrical power generation equipment, generally located at the earth's surface and after which it is then returned into the well for reheating as it travels downward in the extended heat exchanger.
Most irrigation water from deep wells is electrically pumped, and the cost of the electric power used for this purpose is an increasing problem, the energy cost of pumping being estimated to be several times the cost of all other energy uses combined on land so irrigated.
Accordingly, there is a need to provide a cost effective energy efficient means for pumping deep well irrigation water to the surface, especially in remote areas where electrical costs which may include the cost of installing electric lines to the area become prohibitive.